Fixes: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=131569
Dead lock in bridge when removing device interface module. br_del_if
assumes br->lock not held.

This fixes case of:
	brctl addbr b0
	brctl addif b0 eth0
	rmmod eth0
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>